The quantum key distribution (QKD) technology is a technology in which keys enabling cryptographic data communication are shared in safety between a transmission node (a quantum key distribution system transmitter), which successively transmits single photons, and a reception node (a quantum key distribution system receiver), which receives single photons.
In a communication system in which quantum cryptography is used, there are times when the generation rate for generating keys and the arrival rate of the transmitted and received data undergoes fluctuation. In such a situation too, it is necessary to configure a secure communication system to a maximum extent using the finite resources (such as memory resources and communication resources).